Samuel King is the person who made the Facebook post.
He worked at Ruby Tuesday at the mall where the killer worked at GNC.
They were not high school friends.
King made this Facebook post:
I cant believe i knew this dude
. He worked at GNC at the treasure coast mall when i was at Ruby Tuesdays and he Graduated from the same high school in 2004"
After that he got contacted by a bunch of media outlets and shared similar quotes to the one you cited about him coming into the restaurant sometimes and seeming amiable.
If you read the rest of King's Facebook wall, you will see that he barely knew the person, was not even sure they want to the same high school until checking a yearbook, and received responses from others who did remember him from high school and describe him in completely different terms.
King responds to one poster in particular who painted the killer as a violent, nasty person when they were in high school together. This person rode the bus with him every day, he said. King's response was that the killer seemed friendly when he came into the Ruby Tuesday's at the mall, and he hadn't seen that side of him.
If you are genuinely interested in learning the facts, do a little research of your own, and don't take everything at face value.